There are multiple types of thermometers, including hand held electronic thermometers and glass-tube mercury thermometers. The glass-tube mercury thermometers have gradated scales colored or etched into the glass tube and once the mercury rises and settles in the glass tube due to the temperature of the patient, a user can read the temperature from the scale, calibrated for Fahrenheit or Centigrade. Glass-tube thermometers have a number of drawbacks, including the difficulty of reading a temperature from the gradated scale based on the mercury level.
As an improvement, hand held electronic thermometers have been introduced. In the basic electronic thermometer design, a temperature sensing element is connected to a combined, battery-powered computing and display element. The display element is typically a viewing window provided for the temperature display wherein the temperature is displayed numerically in either Fahrenheit or Centigrade. The multi-segment liquid crystal display (LCD) displays of the electronic thermometers are simple to read and can provide a patient's temperature in tenths of a degree.
However, regardless of the means to display the patient's temperature, the user still must remember the proper temperature ranges for normal, warm and fever conditions. Furthermore, these ranges may vary depending upon one or more traits of the patient, such as age, or upon a measurement location, such as oral, rectal, underarm, forehead, behind the ear, etc. For example, it is known that the temperature range associated with a normal body temperature, a low fever, and a high fever can vary with the age of the patient. Newborns (e.g., about 0-3 months) have a range of normal body temperature of 97.3° F. to 100.3° F., and have fever (including high fever) at ≧100.4° F. Because infancy is a critical age for fever, any fever at a temperature≧100.4° F. is considered severe. On the other hand, toddlers (e.g., about 3-36 months) have a range of normal body temperature of 96.6° F. to 100.5° F., a low fever range of ≧100.6° F. to 102.2° F., and a high fever range of >102.2° F. Older persons (e.g., age greater than 36 months to adulthood) have a range of normal body temperature of 95.7° F. to 99.9° F., a low fever range of ≧100.0° F.-103.0° F., and a high fever range of ≧102.2° F. Typically a user must consult a guide or chart to determine if the temperature read poses a threat to the patient.
Additionally, while an electronic thermometer is easier to read than a glass-tube thermometer, it can still be difficult to read for those with poor vision. Thus, conventional thermometers lack a cost-effective, easily identifiable indication of the measured temperature.
U.S. Pat. No. 7,350,973 to Craig et al. (“Craig”) discloses a color changing thermometer with a backlight and a method for lighting the backlight. The thermometer has a temperature sensing tip and a processor that takes temperature readings and determines a sensed temperature reading of a living being from the temperature sensing tip. The thermometer also includes a display and a backlight for lighting the display. The backlight is activated upon a command from the processor and the processor determines whether a decrease in the temperature readings exceeds or is equal to a predetermined threshold in order to activate the backlight. The method embodiment can includes the steps of using the processor to monitor a temperature change indicated by a temperature sensing element. The processor then detects a temperature decrease and activates a first color light emitting element to backlight a display if the temperature decrease exceeds or equals a predetermined threshold.
U.S. Pat. No. 5,829,878 to Weiss et al. (“Weiss”) discloses a thermometer that lights a backlight only on the detection that the temperature reading is complete. If the temperature reading is not completed, the backlight will not be activated. Thus, if the patient accidentally interrupts the reading, the patient will not receive the benefit of the backlight to enable them to see the display. Also, in one embodiment, Weiss' thermometer shuts the backlight off after a predetermined time. If the patient leaves the thermometer in place after the reading longer than the predetermined time, the patient will not get the benefit of the backlight when the patient actually reads the displayed temperature.
In an alternate embodiment, Weiss discloses that the backlight does not shut off until the on/off switch is pressed. This can lead to a drain on the battery and lower the service life of both the battery and the thermometer. The thermometer can be left in the patient for a significant amount of time, if the caregiver is away from the patient attending to other matters. Weiss' thermometer will be backlit the entire time, draining the battery unnecessarily.
A number of U.S. patents disclose thermometers with audible alarms if a patient's temperature is high enough to indicate a fever or once the reading is completed. For example, U.S. Pat. No. 5,165,798 to Watanabe describes an electronic thermometer with an electronic buzzer that is used to indicate the completion of a temperature measurement. Watanabe does not disclose an indicator based on the specific temperature of the particular patient.
U.S. Pat. No. 5,923,258 to Tseng discloses an electronic thermometer designed to display a digital temperature signal under all temperature reading conditions. Tseng then produces a fever alarm indication by optionally flashing the temperature readout and/or sounding a buzzer. Thus, if the patient does not have a fever, the user must still read the display to determine the temperature of the patient. Tseng does not provide audio or visual signals for any other temperature range.
Visual signals identifying the relative temperature of an engine's cooling water are also known. U.S. Pat. No. 6,778,095 to Lo discloses pointer-type meters for vehicles and linking a gradated color scale to the reading determined by the meter. As an initial point, Lo does not relate to thermometry for living beings. Further, Lo does not sense the temperature of the water directly, but senses the displacement of the pointer needle and lights the appropriately colored light. Lo must sense the physical displacement of the pointer to allow the system to be interchangeable with any pointer-type meter. Thus, Lo requires a pointer-type meter and triggers the illumination indirectly by reading the physical displacement of the pointer and not the actual temperature.
U.S. Pat. No. 6,441,726 to Voto et al. (“Voto”) also discloses a warning system for a vehicle instrument cluster wherein the gages can be backlit or have a gradated color scale. The colored lights can be steady on/off or can flash. As with Lo, Voto does not relate to thermometry for living beings. Additionally, Voto does not replace the standard display, but illuminates the standard gauges in a vehicle instrument cluster. Thus, the user may be confronted with a confusing display of both analogue and colored visual stimuli.
Further, using either Lo's or Voto's inventions in a thermometer for living beings is both size and cost prohibitive, since both a readout display and a colored scale display must be included. When included in the cost of a vehicle, the additional cost for the visual system is nominal. However, for a thermometer designed for living beings, it can be a substantial proportion of the cost to include both displays.
Thus, there is a need in the art for a low cost, easy to read, colored visual display for a thermometer meant for living beings.
Further, there is a need in the art for a low cost, easy to read, colored visual display for a thermometer meant for living beings that activates the backlight once the thermometer is removed from the patient.